The present invention relates generally to the field of magnetic data storage and retrieval systems. In particular, the present invention relates to a magnetic read head for use in a magnetic data retrieval system that has a magnetoresistive read sensor with an extended sensing layer to increase its read sensitivity.
Magnetic read heads are positioned over a magnetic disc that is rotated at a high speed. The heads are supported over a surface of the magnetic disc by a thin cushion of air produced by the high rotational speed. This surface is called an air bearing surface. The magnetic read head retrieves magnetically-encoded information that is stored on the disc, and is typically formed of several layers that include a top shield, a bottom shield, and a magnetoresistive read sensor positioned between the top and bottom shield.
A time-dependent magnetic field from the disc directly modulates a resistivity of the read sensor by causing a magnetization of the read sensor to rotate. The change in resistance of the read sensor can be detected by passing a sense current through, and measuring the voltage across, the read sensor. The resulting signal can be used to recover encoded information from the disc.
The top and bottom shields are generally placed on either side of the read sensor to ensure that the read sensor reads only that information which is stored directly beneath it on the magnetic disc. Regular increases in areal densities of magnetic media have made it necessary to regularly decrease the spacing between the shields positioned on either side of the read sensor. This decrease in spacing between the shields has had the negative effect of decreasing the efficiency and read sensitivity of the read sensor, since magnetic flux emanating from the disc reaches a smaller portion of the read sensor.
This decrease in efficiency can be counteracted by decreasing a stripe height of the read sensor, that is, a length of the read sensor along its side normal to the air bearing surface. However, decreasing the stripe height of the read sensor increases the effects of self-demagnetization fields acting on the sensor. The self-demagnetization fields are a consequence of poles generated at a front (near the air bearing surface) and back of the sensor. These fields decrease the read sensitivity of the sensor by decreasing the amount of rotation of the magnetization of the sensor when acted upon by a magnetic field from the disc. An increased stripe height can substantially minimize the effects of these self-demagnitization fields.
Therefore, there is a need for a magnetic read sensor having an increased stripe height to minimize these self-demagnitization effects and to minimize current shunting away from a sensing portion of the sensor.
The present invention is a magnetic read head having an air bearing surface, a magnetoresistive sensor, an insulator layer, and first and second current contacts. The magnetoresistive sensor has a first portion adjacent to the air bearing surface and a second portion distal from the air bearing surface. The first and second current contacts are positioned in electrical contact with opposite edges of the first portion of the magnetoresistive sensor, and the insulator layer is positioned between the second portion of the magnetoresistive sensor and each of the first and second current contacts. The first portion of the magnetoresistive sensor functions primarily as an electrically active region and the second portion of the magnetoresistive sensor functions primarily as an electrically inactive region.
The magnetic read head of the present invention minimizes both a self-demagnetizing effect of the magnetoresistive sensor and current shunting away from a sensing portion of the magnetoresistive sensor. The magnetic read head thereby achieves an enhanced read sensitivity.